Gut Microbiota Metabolism of Bile Acids Could Contribute to the Bariatric Surgery Improvements in Extreme Obesity

Abstract

Bariatric surgery is the only procedure to obtain and maintain weight loss in the long term, although the mechanisms driving these benefits are not completely understood. In the last years, gut microbiota has emerged as one of the drivers through its metabolites, especially secondary bile acids. In the current study, we have compared the gut microbiota and the bile acid pool, as well as anthropometric and biochemical parameters, of patient with morbid obesity who underwent bariatric surgery by two different techniques, namely Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). Gut microbiota populations differed after the respective procedures, particularly with respect to the Enterobacteriaceae family. Both techniques resulted in changes in the bile acids pool, but RYGB was the procedure which suffered the greatest changes, with a reduction in most of their levels. Blautia and Veillonella were the two genera that more relationships showed with secondary bile acids, indicating a possible role in their formation and inhibition, respectively. Correlations with the anthropometric and biochemical variables showed that secondary bile acids could have a role in the amelioration of the glucose and HDL-cholesterol levels. Thus, we have observed a possible relationship between the interaction of the bile acids pool metabolized by the gut microbiota in the metabolic improvements obtained by bariatric surgery in the frame of morbid obesity, deserving further investigation in greater cohorts to decipher the role of each bile acid in the homeostasis of the host for their possible use in the development of microbiota-based therapeutics, such as new drugs, postbiotics or probiotics.

Keywords: Enterobacteriaceae; bariatric surgery; bile acids; gut microbiota.

Figure 1

(a) Heatmap of the changes in the relative abundance of the microbiota profile at Phylum, Family and Genus levels of the two bariatric surgery procedures tested, Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). Differences in percentage are shown. * Indicates changes within the RYGB procedure, $ indicates changes between procedures. (b) Bar plots of the statistically significant bacteria from the previous heatmap.

Figure 2

Heatmap of the bile acids fold changes in the two bariatric surgery procedures studies. (a) Total bile acids changes. (b) Primary bile acids changes. (c) Secondary bile acids changes. Changes are shown as fold changes within each procedure; * indicates statistical differences (p < 0.05) between procedures, $ indicates a statistical tendency (p < 0.10) between procedures.

Figure 3

Heatmap of the Spearman correlations between bacteria of interest and secondary bile acids. * Indicates p < 0.05.

Figure 4

Heatmap of the changes in the metabolic pathways inferred by a Picrust analysis of the 16S rRNA sequences. Metacyc pathways of interest are depicted, as well as their super-classes of entity. Additional information about each pathway-ID can be found in the Supplementary Table S1 in Supplementary Materials.

Figure 5

Heatmap of the Spearman correlations between changes in anthropometric and biochemical variables with the fold-changes in secondary bile acids. * Indicates p < 0.05.